The present invention relates generally to the field of traffic control and more particularly to notifying vehicles and/or pedestrians of an approaching priority vehicle with directional information.
Traffic lights, also known as traffic signals, traffic lamps, traffic semaphore, signal lights, stop lights, robots, and traffic control signals, are signaling devices positioned at road intersections, pedestrian crossings, and other locations to control and coordinate traffic flow to ensure smooth and safe movement. The normal timing of the traffic signal (i.e., time plans that sometimes range from 35 seconds to 120 seconds in length) may be interrupted through traffic signal preemption. Traffic signal preemption (e.g., traffic signal prioritization) is a type of system that allows the normal operation of traffic lights to be preempted (i.e., replaces normal traffic light timing sequence with an altered timing sequence based on notification of an event occurring that takes precedence over the current conditions). For example, an emergency vehicle manipulates traffic signals by halting conflicting traffic and allowing the emergency vehicle right-of-way. Additionally, traffic signal preemption can also be used by light-rail and bus rapid transit systems to allow public transportation priority access through intersections, or by railroad systems at crossings to prevent collisions. Traffic preemption devices can be installed on road vehicles, integrated with train transportation network management systems, or operated by remote control from a fixed location, such as a fire station, or by a 9-1-1 dispatcher at an emergency call center.
Traffic preemption devices are implemented in a variety of ways (e.g., acoustic sensors, line-of-sight, Global Positioning System (GPS), radio based, etc.). Traffic preemption systems equipped with acoustic sensors override the traffic signal upon detection of a specific pattern of tweets or wails from the siren of an emergency vehicle. Line-of-sight traffic signal preemption systems send a narrowly directed signal forward towards traffic lights from individual equipped vehicles, in an attempt to obtain right-of-way through controllable intersections prior to arrival at the intersection. Traffic preemption systems implemented with a Global Positioning System (GPS) determine a location of the activating vehicle, a direction in which the vehicle is heading, identify which traffic lights to preempt, and an ability to activate the identified traffic lights. Radio-based traffic-preemption systems are installed in vehicles, and use a local, directional, short-range radio signal in which the operating range can be adjusted to activate only nearby, traffic signals, or traffic signals at greater distances.